The present invention relates to an armature coil, and in particular to an armature coil which is suitable for use in high-speed rotary electric machinery such as electric motors and generators.
As a stator coil assembly for generating a rotating magnetic field in rotary electric machinery, it is known to place coils for U, V and W phases in two layers on the inner circumferential surface of a hollow cylindrical slotless stator core via an insulating layer. These coils may consist of a plurality of twisted wires, and may be impregnated with resin so as to be molded into a desired shape. Such examples are disclosed in Japanese patent laid-open publication No. 1-252134A and U.S. Pat. No. 5,313,131, and the contents of these prior patent publications are hereby incorporated in this application by reference.
In such an arrangement, the coils are molded into a plurality of coil blocks and these coil blocks are combined into a cylindrical shape while providing such that individual coils for generating a rotating magnetic field corresponding to the U, V and W phases are arranged as required. Also, the coil wire strands tend to be more dense in the inner layer and more coarse in the outer layer so that the space ratio of the copper tends to be limited, and the copper loss cannot be reduced as much as desired. Also, because the coil wires are distributed relatively coarsely in the outer layer, the removal of heat from the outer layer cannot be effected as efficiently as from the inner layer. In high speed electric generators and motors, eddy current loss and circulation loss as well as copper loss limit the efficiency, and such losses are also desired to be minimized.
In view of such problems of the prior art, a primary object of the present invention is to provide an improved armature coil which is suitable for use in high-speed rotary electric machinery such electric motors and generators.
A second object of the present invention is to provide an armature coil suitable for use in slotless rotary electric machinery.
A third object of the present invention is to provide an armature coil which can minimize various losses.
A fourth object of the present invention is to provide an armature coil which provides a high cooling efficiency.
According to the present invention, at least most of these objects and other objects can be accomplished by providing an armature coil for a rotary electric machinery such as electric generators and motors including a plurality of identical coil blocks each formed by a plurality of turns of an elongated conductor so as to correspond to different phases, characterized by that: each of the coil blocks includes two groups of axial sections which are diametrically opposed to each other and curved sections joining the two groups to each other at each axial end, the axial sections of one of the groups being disposed in an inner cylindrical layer while the axial sections of the other of the groups are disposed in an outer cylindrical layer which is coaxial with the inner cylindrical layer; and the coil blocks are combined with each other by circumferentially shifting one coil block from another in such a manner that the axial sections are arranged circumferentially along the inner and outer cylindrical layers one next to another.
This allows the coils for U, V and W phases to be arranged evenly over the entire circumference, and the copper space ration can be maximized. In particular, if the axial sections disposed in the inner cylindrical layer are smaller in number than those disposed in the outer cylindrical layer by one, the copper space ratio can be maximized even when the cross sectional shape of the conductor is uniform over its entire length.
If each of the coil blocks is formed by a Litz wire conductor which is molded into a prescribed cross sectional shape, the eddy current loss can be minimized, and the conductor can be freely formed into a desired shape with ease. The production efficiency can be further improved by using a substantially cylindrically shaped insulator assembly for retaining the conductors in place.
If the insulator assembly defines a plurality of axially extending gaps in cooperation with the conductor, or a plurality of axially extending gaps are defined between adjacent axial sections of the conductors for conducting cooling fluid therethrough, the cooling of the coils can be effected in both efficient and highly controllable manner.